Antifoam material in wax



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for packaging comestibles. example of an application of this type is exemplifiedin r 3,132,959 ANTIFOAM MATE IN WAX M. Shadan, Ponca City, Okla, assignor to Continental Oil Company, Ponca City, Okla, a corporation of. Delaware No Drawing. Filed June 10, 1960, Ser. No. 35,136

5 Claims. (Cl. 106-270) This invention relates to wax Compositions useful in I surface coating applications generally and especially adapted for the coating or lining of paper containers and the'like wherein comestibles are temporarily stored. More particularly, this invention concerns oxidation-stabilized parafiin wax compositions which in the molten or fluid state exhibit improved non-foaming tendencies. The present invention further relates to a process for preparing the said wax compositions.

Because of their outstanding resistance to water and overall excellent chemical resistance and inertness, waxes are "extensively utilized to coat paper containers designed Probably the most notable the packaging of dairy products, particularly milk. in carrying out the coating procedure, it is customary to dip a fiat blank of the carton container into a molten bath of the wax and thereupon shape the blank after the wax deposit has suitably solidified.

j Most'waxes, irrespective of their source or origin, exhibit foaming tendencies in the molten state, especially when liquid baths thereof are subjected to the degree of mechanical agitation normally occurring in the various coatingopera-tions. Generally, the character of the foam eipcountered in molten Wax compositions is sufliciently stable so that when the wax solidifies on the surface of the pa'perlthere results portions thereof having thin or otherwise inadequate covering of the wax. If these faulty areas are on the surface forming the inside of the container, it is likely that the liquid contents will ultimately penetrate the paper at these areas thereby weakening the paper to the extent that leakage develops. On the other hand if the foam covers the outside of the container,

the functional purpose of the container may not be adver'selyaifected but nevertheless in many of such instances the containers have to be disposed of as rejects because of their unattractive appearance In current commercial wax coating practices of the type hereinabove mentioned a petroleum, and morespecifically, a paraffin wax is favored since this type of wax is readily available and comparatively inexpensives This invention, however, is not limited to the use of a. petroleum wax but can be beneficially utilized to inhibit the foaming tendencies of other type waxes and mixtures thereof with a petroleum wax. a

One of the principal objects of the present invention is to provide a non-foaming wax composition.

Anotherv object of this invention is to provide a parafiin wax composition containing an effective dispersion of a defoaming agent and an antioxidant, the latter serving a dual purpose of stabilizing the wax toward oxidation upon any prolonged contact with air and of uniquely facilitating the effective dispersion of the defoamant throughout the wax composition.

Other objects and advantages of this invention will become. more apparent to those skilled in the art upon aconsideration of the detailed discussion and example setforth hereinbelow.

1 Sinceparafiin wax or a wax composition containing a major portionof parafiin wax is. viewed as the preferred the crude source, the portion of the Patented May 12, 1964 ering the procedures ordinarily involved in producing a Parafiin waxes are the wax constituents occurring in various fractions of certain crude petroleums. They manifest melting points in a range of about 47 to 65 C. and Saybolt viscosities in the range of from about 35 to 45 S.U. at 210 F., and are further physically characterized by crystallizing into large, well-formed distinct crystals of the plate and needle ty'pes.

The precise physical characteristics of a parafiin wax may These paraffin rich fractions are normally liquid at 80 to 7 100 F., whereas cooling below this range readily effects precipitation of the wax. This limited solubility characteristic at low temperatures is availed of to segregate most of the wax content. The precipitate is then filtered by any' of several conventional methods in a process termed pressing whichprocess yields 'a filtrate called slack wax. Slack wax normally contains from about 20 to 40% oil content. Subsequent to the pressing operation, the slack oil is sweated. Sweating is accomplished by heat treating the slack wax whereby the oil will drain or sweat out of the-solid wax as the temperature is slowly raised. The sweating operating yields :a crude scale wax containing about 2% oil and melting at about 122- 124 F. Fully refined paraflin wax is then obtained by merely further sweating the crude scale wax to a specific melting point range followed by treatment with a suit-able adsorbent such as fullers earth, bonechar, bauxite and the like. The fully refined product is substantially free of oil. a The use of the highly refined type of paraffin wax is not mandatory in the various coating operations mentioned hereinabove. Thus, mixtures of therefined with slack wax or crude scale wax may be advantageously e.g., beeswax, carnauba wax, etc.- Also, microcrystalline waxes can be advantageously used in combination with paraffin wax. r

In view of the above, the term paraflin wax composition used herein and in theappended claims broadly contemplates those above-described compositions or mixtures having genenal utility in the coating, arts. However, a

composition in the practice of this invention, a mention willbe made here of the various gnades and types coming within the scope of the term paraffin wax as contemplated herein. This can be best accomplished by briefly considpreferred wax composition for practicing the present invention is one wherein the panaflin wax content is" at least 50% of the total weight of the composition.

In accordance with my invention, the foaming tendencies of a paraflin wax composition can be substantially and in many instances completely eliminated by incorpo rating into. the wax relatively minute quantities of a homogeneous admixture of a polymeric vinyl ester defoamant and an oxidation inhibitor comprising 2,6-ditertiary. butyl paracresol. As is known to those skilled in this art, the eifective antifoamants for wax compositions, including the polyvinyl esters of this invention, are all substantially insoluble in the wax. Consequently, in order to assure suitable reduction of foaming tendencies, the defoamant must be intimately and completely dispersed throughout the wax composition. I have discovered that this required degree of dispersion of the antifoamant can be simply and readily effected by combin ng the antifoamant with the said antioxidant material in which the defoamant is soluble and then admixing this homogeneous combination with a liquefied wax composition. As mentioned previously, the ditertiary butyl paracresol not only serves to effect proper distribution of the defoamant through the wax composition but additionally minimizes any oxidation tendencies the wax may have upon standing in contact with air. I

In order to achieve the advantages of this invention, the defoamant must be dispersed in the wax composition as a solubilized mixture with the antioxidant, specifically ditertiary butyl paracresol. It has been noted that if for instance the antioxidant is solubilized within and thus uniformly distributed throughout the wax composition, that this procedure will not permit the subsequently added defoamant to be beneficially incorporated in order to realize the advantages of this invention.

The defoamants used in the practice of this invention include those polymeric vinyl esters which are disclosed and claimed in US. Patent 2,841,553. These defoamants can be described for most part as a vinyl ester polymer consisting of a vinyl ester of a fatty acid having an average of from 4 to 8 carbon atoms in the acid portion of the polymer and exhibiting a specific viscosity of from 0.25 to 1.5 at 25 C. as determined for a 10% cyclohexanone solution of said liquid polymer; that is, a solution comprising .10 parts of the polymer and90 parts of cyclohexanone. V

A specific enumeration of the above defined vinyl ester polymers include such as: polyvinyl butyrate, polyvinyl V isobutyrate, polyvinyl n-valerate, polyvinyl isovalerate,

polyvinyl caproate, polyvinyl Z-ethylhexoate, polyvinyl dimethylacetate, polyvinyl n-octoate, etc. each having a specific viscosity characteristic within the range mentioned.

The amount of polyvinyl ester 'antifoamant varies extensively and ranges from about 0.000l% to 0.1% based on the Wax. The exact quantity of the antifoamant utilized will depend on various factors such as the specific nature of the ester employed, the composition of the wax utilized and the like. In general, it is not necessary to use more than about 0.01% of the vinyl ester polymer 'based on the weight of the wax composition. When using the preferred antifoamants, namely, either polyvinyl caproate or polyvinyl Z-ethylhexoate, improved results in accordance with this invention can be obtained by employing amounts of said esters ranging from about 0.000l% to 0.0025 based on the total wax composition.

The amount of 2,6-ditertiary butyl paracresol contemplated for addition to the wax composition are those amounts normally used to effect oxidation inhibition of parafiin wax; These amounts range from'as low as about 0.0005 to generally not in excess of about.0.0l% based on the total wax composition. Within this broad range from about 0.005% to about 0.0025% of the paracresol will often be used. In the practice of this invention, however, the use of the antioxidant is not strictly confined to that of accomplishing oxidation inhibition of the Wax but further serves as a carrier for the defoamant. Accordingly, it is desirable to employ an amount 'of the antioxidant which will effectively solubilize or dissolve the quantity of defoamant used irrespective of whether said amount exceeds that needed to effectively inhibit the wax against oxidation. With this in mind, it is desirable to employ an amount of the inhibitor at least-about equal to the amount of defoamant used. Generally, however, the upper limit of antioxidant used will not exceed about five times the amount of defoamant used. larly, with respect to this aspect it is desirable to employ a higher ratio of the antioxidant to defoamant, namely, in the order of about 4 or 5 to 1, respectively, when employing the lesser amounts of the defoamant contemplated.

More particu- Y The procedure of incorporating the defoamant is important in order to achieve the advantages of this invention. The defoamant used must be dissolved in the antioxidant or the amounts of the respective components of this combination must be compounded in order to achieve the solution of that amount of defoamant capable of dissolving in the amount of antioxidant present. After accomplishing the mixing of the defoamant and antioxidant in accordance with the above, this combination is then thoroughly dispersed throughout the liquefied wax composition.

In order to further illustrate the nature of the present invention, the following example is given in which all parts or percent figures are by weight. It is to be understood that this invention is not limited to the specific details set forth in this example except that such limitations are specified in the appended claims.

EXAMPLE I p The relative effectiveness of polyvinyl caproate and 2,6- ditertiary butyl paracresol and various homogeneous mixtures thereof in reducing foaming tendencies of paraifin wax are demonstrated in this example.

A specimen of a standard stock paper used to prepare milk cartons was provided with a coating of wax by immersing the paper Within a bath of the molten wax. Upon' withdrawing the specimen and solidification of the applied coating the specimen was noted foruniformity of coating and rated accordingly. The ratings were based on numerical values given on a demerit scale ranging from 0 to 8. In this particular system of rating, 8 indicates an excessive amount of faults due to foam.- On the other hand, a rating of 0 indicates that the coating is substantially free of any irregular portions attributed to the presence of foam within the coating bath. The wax used in this series of tests was a paraifin wax having a melting point of about 127--128 F. modified with 15% of a microcrystalline wax. The composition of the various wax coating baths together with the foam ratings for specimens coated therewith are set forth in the following Table I.

Table 1 Percent Percent Foam Polyvinyl DBPO Rate Caproate 0.0 0.0 7 0.0004 0.0015 0 0.05 0.0 5 Coating D 0 .0 0.01 6

'said ester having an average of from 4 to 8 carbon atoms in the acid portion thereof, a 10% cyclohexanone solution of said vinyl ester polymer having a specific viscosity from about 0.25 to 1.5 at a temperature of 25 C.

2. A process for inhibiting the oxidation of a wax composition and stabilizing said composition towards foam formation in the molten state comprising uniformly admixing with the wax composition a homogeneous dispersion of a combination of an oxidation inhibiting amount of 2,6-ditertiary butyl paracresol and fronrabout 0.000l% to 0.1% of a polymer of a vinyl ester of a fatty acid,

said ester having an average of from 4 to 8 carbon atoms in the acid portion of the polymer, a 10% 'cyclohexanone solution of said polymer having a specific viscosity from about 0.25 to 1.5 at a temperature of 25 C.

3. A process for inhibiting the oxidation of a wax com position and stabilizing said composition towards foam formation in the molten state comprising uniformly admixing with the wax composition a homogeneous dispersion of a combination of from about 0.0005 to 0.01% of2,6-ditertiary butyl paracresol and from about 0.0001% to 0.01% of polymer of a vinyl ester of a fatty'acid, said ester having an average of from 4 to 8 carbon atoms in the acid portion of the polymer, a 10% cyclohexanone solution of said polymer having a specific viscosity from about 0.25 to 1.5 at a temperature of 25 C., and wherein Y said combination the weight 'ratio of the 2,6-ditertiary butyl paracresol to said vinyl ester polymer is between about 1:1 to 5:1, respectively.

' 3 T 4. A process for inhibiting the oxidation of a Wax composition and stabilizing said composition towards foam formation in the molten state comprising uniformly admixing with the wax composition a homogeneous dispercosity of from. about 0.25 to 1.5 at a temperature of 25 C., and wherein the weight ratio of the 2,6-ditertiary butyl paracresol to said polymer is between about 1:1 and 5:1, respectively. I

5. A process for inhibiting the oxidation of a wax composition and stabilizing said composition towards foam formation in the molten state comprising uniformly admixing with the wax composition ahomogeneous dispersion of a combination of about 0.0015% of 2,6-ditertiary butyl paracresol and about 0.0004% of a polymeric vinyl caproate, a 10% cyclohexanone solution of said polymer having a specific viscosity of from about 0.25 to 1.5 at a temperature of 25? C.

2,841,558 Fields. July' 1, 1958 Hunter et a1. Feb. 23, 1954 r 

1. A PROCESS FOR INHIBITING THE OXIDATION OF A WAX COMPOSITION AND STABILIZING SAID COMPOSITION TOWARDS FOAM FORMATION IN THE MOLTEN STATE COMPRISING UNIFORMLY ADMIXING WITH THE WAX COMPOSITION A HOMOGENEOUS DISPERSION OF A COMBINATION OF AN OXIDATION INHIBITING AMOUNT OF 2,6-DITERTIARY BUTYL PRACRESOL AND A FOAM DEPRESSANT AMOUNT OF A POLYMER OF A VINYL ESTER OF A FATTY ACID, SAID ESTER HAVING AN AVERAGE OF FROM 4 TO 8 CARBON ATOMS IN THE ACID PORTION THEREOF, A 10% CYCLOHEXANONE SOLUTION OF SAID VINYL ESTER POLYMER HAVING A SPECIFIC VISCOSITY FROM ABOUT 0.25 TO 1.5 AT A TEMPERATURE OF 25*C. 